Thermostatic switch



April 1942- H. w. RIMBACH 2,279,060

THERMOS TATIC SWITCH Filed June 22, 1940 20 7&9

[I .Q. g5 9 10 35 36% w I K Heng/WRM ATTOR 21 fl 19 INVENTOR Patented Apr. 7, 1942 THERMOSTATIC SWITCH Henry W. Rimbach, East Orange, N. 1., assignor to Technioo,

Incorporated, New York, N. Y., a corporation of Delaware Application June 22, 1940. Serial No. 341,881

lClaim.

This invention pertains to that class of electrical switch which opens and closes in response to temperature changes. and which is commonly known as a thermostatic switch.

It is an object of this invention to produce a device which is simple and compact in construction, cheap to manufacture and substantially foolproof in operation.

It is another object to produce a switch which opens and closes-quickly so as to reduce arcing, which results in burning of contact points.

A still further object of the invention is to produce a switch which can be readily adjusted for various temperature ranges and limits.

The drawing illustrates and the specification describes only one embodiment of my invention,

but others will be apparent to those skilled in the art as will other advantages not herein recited.

Looking at the drawing:

Fig. 1 is a plan view of one form Fig. 2 is a side elevation of Fig. 3 is a side elevation ment of the invention; and

Fig. 4 is a side elevation of still a third embodiment.

Looking at Figs. 1 and2. we find a square or rectangular framework l,'made up of a bimetallic strip 2, twisted at I so that the metal on the outside of the frame on the right side, is on the inside of the frame on the left side. One of th metals of the bimetallic strip is shown at 4 and the other at i.

The framework l possesses suflicient springiness and is so constructed that the open ends thereof shown at l and I, tend to move toward each other when spread s'ufiiciently to accommodate links 9 and I therebetween. Opposite edges of links are shaped in the form of a V groove as shown in Fig. 2. The left hand edge of link It is shaped to a sharp edge and the right hand side to a V groove (Fig. 2).

The end 8 of the frame I may be equipped with two bearing points or surfaces I3 and II designed to rest in th left V-shaped groove of the link 9. The pointed and sharpened edge of link Iii is designed to rest in the other V-shaped groove of link 8. The end I of the frame I is formed into two bearing points or surfaces It and I1, which are designed to rest in the right hand V groove of link Ill.

To the underside of link 9 is attached an arm is on the lower end of which is a contact point is adapted to cooperate with stationary contact point 20 to mak and break an electrical circuit.

of the device; the same form; of another embodi- A stop 2i serves to arrest the arm II in its clockwise movement as viewed in Fig. 2.

Fig. 3 discloses a somewhat difi'erent form of theinvention and includes a stationary frame or foundation 30 to which is firmly secured a bimetallic strip II made into a more or less serpentine form as illustrated in the figure. The link 9 carries a bent arm is and on the end of arm 28 is a contact point is adapted to cooperate with stationary contact point 20 to make and break a circuit. 'Themember in acts as a stop for the arm 28 when it moves in a clockwise direction as indicated by the arrow, and thus serves the same purpose as the stop 2| of Fig; 2.

Link I0 is disposed between link 8 and a stationary V-shaped frame member 24 equipped with suitable bearings points, one of which is shown at 21. Links 9 and Ill and the bearing end of member 3| are the same as the links and bearing points heretofore described in relation to Fig. 2. The member 3| is so proportioned that it is slightly compressed when links 9 and III are inserted between its free end and member, and thus normally exerts a pressure on the links 0 and iii in the direction of the member 24.

In Fig. 4, is another embodiment of the invention including a stationary frame member 30, a straight bimetallic member 35 cantilever mounted thereon, links a and Iii and a bearing member 36 attached to an adjustable spring arm 31 which is supported in the frame member 38. The length of the members SI. and 36, and the links 0 and iii are such that when in position a slight strain is imposed on the spring member 31 which normally urges the member 36 toward the bimetallic member 35. Link 9 is equipped with an arm 28 carrying a contact point I! adapted to cooperate with contact point 20. The movement of arm 28 is limited by point 2|! and stop 2|.

Fig. 2 illustrates the position of the various elements of the device after it has been subjected to a relatively low temperature so that the contacts closed. As the temperature I and 8 of the bimetal move in the dicated by the-vertical arrows, and changes take place in acting upon it:

Points A and B move downward and to the right. Point C moves upward to the right. Thus point A moves from a position above an imaginary line connecting points B and C until it lies on the same line. Up to this time the force exerted on link a by link It at point A tends to keep confacts It and 20 together; that is, the vertical component of this force is upward. When point directions inthe following the linkage and the forces rises the ends A comes into line with points B and C, the vertical component of the activating iorce at A becomes zero. The instant the point A moves below this neutral line, the vertical component of the force exerted on link I by link III at point A, becomes downward. This causes the contact arm to snap over to stop 2|.

when the temperature falls, the reverse of this action takes place and the contact I! snaps over to contact 20. It is evident that the switch is operated by a change in direction of the force exerted by the bimetal acting on link 9.

In the device herein disclosed there is no tendency for the contacts to open before the instant oi "snapping." On the contrary, as the device moves from "cold" to neutral, not only do the forces tend to keep the contacts closed, but the whole linkage moves in such a direction as to tend to press the contacts together.

The device is very flexible, and it can be made to respond to a wide variety or temperature ranges and limits. It the links 8 and I0 are made short, it will operate within a narrow temperature range, and, of course, if they are lengthened, operation will be through a wider range. It the device is constructed so that point A is a relatively great distance above the imaginary line connecting points B and C when the bimetal is cool and the contacts together, then a: higher temperature will be required to cause the contacts to open than it the point A is more nearly on line BC. It the distance (Pig. 2) between stop 2| and contact 2c is decreased, the device will operate within a smaller temperature range and vice verse. In Fig. 2 if contact 2|) and stop 2| are moved to the left (without changing the distance between them), the temperature range remains substantially the same (i. e. the number 01' degrees between on and "013"), but the operating temperatures are lowered. 01 course, it these are moved to the right the temperatures are raised.

It is thus obvious that applicant's switch is capable of many adjustments to make it suitable for nearly any kind 01' service within its capacity.

II it is desired to control low temperatures with this device, as would be desirable in the refrigeration industry, the stop 2| and contact 20 (Fig. 2) are interchanged.

I wish it to be understood that I do not limit myself to the exact details of construction shown and described, as my invention is obviously capable of various modifications.

I claim:

, In a thermostatic switch, a substantially straight bimetallic member formed with a pivot point at one end thereof, a spring actuated movable pivot point, a pair of links supported between said pivot points of such size and proportions as to normally cause said movable pivot point to be urged in the direction of the bimetallic pivot point, and a switch arm on one of said links and means for limiting its movement in both directions.

HENRY W. RIMBACH. 

